The design requirements on wet and dry vacuum cleaners are for deep groove ball bearings that can provide protection against ingress of brush dust contamination and humidity. Where brush dust is the contaminant bearings are fitted with metal shields incorporating a special labyrinth design. In conditions where humidity is a problem, heavy contacting rubber seals are the preferred solution.

In those designs where higher speeds are required the internal radial clearance is optimised and grease selected that can cope with the operating conditions.